Oh, now I get you.
But it's not a bug. The thing is working as intended - which absolute crap. That's why I said, whoever had that idea must not work on video games anymore. It's like you have to search for the keyhole in a car because it appears on random positions anytime you open the door
So indeed you can't see which artifact in which Rift mission is missing. If you haven't keep track of each artifact you collected and noted every place where you collected it, it'll be hard to get it.
However you can still start with such a list now. Look at the
thread here for the two Belle Epoche maps (
map1 and
map2). Then make a list of these 8 locations. Go to the 4 locations per mission and note which artifact you have collected. If you got all 4 of one Rift, the missing artifact is in the other one. It will appear, you just have to waste a lot of time ...